The subject matter disclosed herein relates to failure prevention and, in particular, systems and methods to avoid single point failures.
Gas turbines, used in the generation of power, draw in air from the atmosphere and a fuel as inputs. The fuel can be gas, liquid or a combination of gas/liquid fuel. The fuel and air are combined and combusted to provide the driving force causing the turbine's rotor to rotate. As is known in the art, the power generated from gas turbines can be controlled by controlling a rate at which the fuel and air are provided to the turbine.
Inlet air from the atmosphere passes through an inlet guide vane (IGV) and then enters a compressor. Inlet airflow rate can be adjusted by changing a vane angle of the IGV. Fuel flow is controlled by a set of flow control and pressure control valves. The flow control and pressure control valve position can be measured by two or more variable differential transformers (VDTs) per valve depending on configuration. In general, the VDT's are used to measure the position of the valve. The VDT's can be either linear VDTs (LVDTs) or rotary VDTs (RVDTs) VDT's, in general, include an excitation (primary) coil and one or more output coils. In some cases, when the configuration uses two VDTs, the highest value is considered in control and protection algorithms. In cases where three VDT's are used to monitor the position of a single valve (i.e., a triple modular redundant (TMR) system) it is common to use a median value of the three reported positions in control and protection algorithms.
In order to operate the turbine in a desired manner, the user specifies a power output level. From this level, control algorithms determine the fuel and air required to meet the output level. The fuel and air requirements can be converted to valve and IGV positions and the positions are monitored by the VDTs. Of course, the valve and IGV positions can be changed to more closely tune the turbine to a desired power output.